Java AWT国际化动态

Question

I am creating a Prototype application, which should support Japanese Locale and English Locale. There should me Menuitem to select Japanese or English. and accordingly application should show all it's lables buttons text in Japanese or English.

I developed using Netbeans internationalization support. if i pass VM arguments as -Duser.language=ja -Duser.country=JP, application shows Japanese text on lables and buttons etc.

if i pass VM arguments as -Duser.language=en -Duser.country=IN, application shows English text on lables and buttons etc.

this works fine. but how to make it dynamic. so that no need to restart the application with VM arguments.

Answer 1

I think this is a rather general question about handling the dynamic translations.

Generally I know of three ways to do it.

1. Every label or text set in the application has to register a listener to an event you would issue when the language changes. In the listener you would read the new locale and load the proper string from your bundle.
2. Traverse the component hierarchy down from the window and translate all texts found on the way.
3. Set the other locale programatically, then destroy and recreate the GUI.

Maybe it's a sad thing to say, but all these options need general and rather large changes in the program code.

Of these, I would prefer 1. I actually have written some components like JLocalizedLabel receiving the label as label an instance of LocalizedString instead of String. With this, you don't even need the event listeners, it is sufficient to repaint the component and the change is done. But this way it only works for the main text on a button or label, whereas for eg tooltip texts or so you still need the event listeners.

This is how it could look like (just an example):

public class JLocalizedLabel extends JLabel
{
   /** The localized string to display. */
   protected LocalizedString              string;

    public JLocalizedLabel(LocalizedString string, Icon icon, int horizontalAlignment)
    {
        super(string.toString(), icon, horizontalAlignment);
        this.string = string;
    }

    @Override
    public String getText()
    {
        if (string == null)
            return "";
        return string.toString();
    }

    @Override
    public void setText(String text)
    {
    }

}

And the LocalizedString class:

public class LocalizedString
{

    /** The key to search for in the resource bundle. */
    protected String                                 key;
    /** The cached text to display. */
    protected String                                 text;
    /** The name of the resource bundle to use. */
    protected String                                 bundleName;
    /** The cache of resource bundles for the active locale. */
    private static Hashtable<String, ResourceBundle> bundles = new Hashtable<String, ResourceBundle>();
    /** The cached application locale. */
    private static Locale                            locale  = /* get the current locale */

    static {
        //install the locale change listener
        ServiceLocator.get(ConfigurationManager.class).get()
                .addPropertyChangeListener("locale", new PropertyChangeListener() {
                    @Override
                    public void propertyChange(PropertyChangeEvent evt)
                    {
                        bundles.clear();
                        locale = (Locale) evt.getNewValue();
                    }
                });
    }

    /**
     * Create a localized string by reading <code>key</code> from a resource bundle with name <code>name</code>.
     * 
     * @param bundleName The name of the resource bundle (the bundle will be retrieved by calling
     *            <code>ResourceBundle.getBundle(bundleName, locale)</code>)
     * @param key The key to search for in the resource bundle.
     */
    public LocalizedString(String bundleName, String key)
    {
        this.key = key;
        this.bundleName = bundleName;
        updateText();
        installLocaleListener();
    }

    /**
     * The locale has changed, so reload the text from the bundle.
     */
    protected void updateText()
    {
        try {
            text = getBundle().getString(key);
        } catch (MissingResourceException e) {
            text = "";
        }
    }

    /**
     * @return The resource bundle associated with this localized string in the current locale.
     */
    protected ResourceBundle getBundle()
    {
        if (bundles.get(bundleName) == null) {
            bundles.put(bundleName, ResourceBundle.getBundle(bundleName, locale));
        }
        return bundles.get(bundleName);
    }

    /**
     * Return the currently active locale.
     * 
     * You can override this in child classes to reflect another locale. Then you should also override
     * {@link #installLocaleListener()}.
     * 
     * @return The currently active locale.
     */
    protected Locale getLocale()
    {
        return locale;
    }

    /**
     * Add a listener to the active configuration that will call {@link #updateText()} every time the locale has
     * changed.
     * 
     * You can override this in child classes to reflect another locale. Then you should also override
     * {@link #getLocale()} .
     */
    protected void installLocaleListener()
    {
        ServiceLocator.get(ConfigurationManager.class).get()
                .addPropertyChangeListener("locale", new PropertyChangeListener() {
                    @Override
                    public void propertyChange(PropertyChangeEvent evt)
                    {
                        updateText();
                    }
                });
    }

    @Override
    public String toString()
    {
        return text;
    }
}